Toluenediamine is made commercially by hydrogenating dinitrotoluene manufactured by the mixed acid method. In such process toluene is contacted with nitric acid in the presence of sulfuric acid under conditions for producing a reaction product containing primarily a 2,4- and 2,6-dinitrotoluene isomer mixture (65-80% 2,4- and 20-35% 2,6-). The dinitrotoluene is recovered and then contacted with hydrogen in the presence of a hydrogenation catalyst, e.g., a nickel catalyst. On completion of the hydrogenation, the reaction product containing toluenediamine is distilled under reduced pressure and elevated temperature (360.degree. to 390.degree. F.) and any lights, water, toluidine, orthotoluenediamine and byproducts removed. Following distillation, the meta-toluenediamine isomer mixture is recovered from the bottom of the column at a temperature at about 390.degree. F. and passed to a product cooler where the temperature is reduced to about 230.degree.-250.degree. F. and the pressure elevated to atmospheric. The resulting meta-toluenediamine isomer mixture is sent to storage.
Toluenediamine is a high melting aromatic diamine having a melting point of about 105.degree. C. or 220.degree. F. Because of its high melting point, storage and transport becomes difficult, particularly in large containers such as encountered on ships. If the meta-toluenediamine isomer mixture is allowed to convert to a solid, the aromatic diamines may undergo degradation on remelting due to poor heat transfer. Not only is there a problem with stability, there is the problem of remelting a large solid block because of such poor heat transfer. Attempts have been made to granulate toluenediamine for remelting, but such attempts also have remained unacceptable because of poor heat transfer between the solid granules. The toluenediamine isomer mixture then is typically stored in small vessels and transported by truck or transport vehicles equipped to maintain toluenediamine at a temperature in excess of its melting point.
Long term storage and transport in large containers such as present in ocean-going vessels is extremely difficult. One problem association with such storage and/or transport is in the lack of equipment necessary to maintain the stored toluenediamine at a temperature above its melting point. Aside from the equipment requirements for maintaining the toluenediamine at a temperature above its melting point, there is the operational energy cost component associated with the storage and transport process when maintaining the temperature of the toluenediamine above its melting point for an extended period of time.